Surgeon says more clinical studies are needed to determine the future of PRP

A classification system based on activation and white cell composition may help define the use of PRP.

SAN FRANCISCO — New research and the advent of a classification system may help clarify the present and future use of platelet-rich plasma, according to one surgeon.

“What I would suggest is orthopedic surgeons are revolutionaries in regenerative medicine, and we need to embrace this opportunity to change, not just our own specialty, but others,” Allan Mishra, MD, said during a feature lecture at the 2011 Annual Meeting of the Arthroscopy Association of North America. “Platelet-rich plasma (PRP) is not a new concept or commodity, it is just how we use it.”

Although PRP has been mentioned in the literature as early as the 1950s, Mishra noted that the bank of clinical information regarding the use of PRP is limited.

Part of the issue is hype vs. reality, he said. “A lot of elite athletes have been treated with PRP, but we do not know for sure what they have been treated for or how they are doing,” Mishra said.

Allan Mishra

Mishra noted that organizations like Major League Baseball, the National Football League and the National Basketball Association have made presentations about PRP. However, “more collective data for these elite athletes is needed and important.”

Defining PRP

He called for orthopedists to be more involved in defining PRP. “What is PRP?” Mishra asked. “Right now, the lay literature is defining that, and I think we have an obligation to do a better job deciding what PRP is.”

Mishra noted that while PRP is “essentially an autologous soup of cytokines” with relative ease of use and availability at point of care, the real question is whether it is effective. PRP, he noted, is a generic term, and a more precise definition is needed. Such a definition should include activation status, platelet concentration and the use or lack of white blood cells.

“If you activate prior to use, you are pushing out all the growth factors and creating a gel or some form of material you can suture, but if you do not activate it, it will be activated by in vivo collagen,” Mishra said, adding that PRP activated with collagen has been shown to demonstrate higher rates of growth factor release.

White blood cells are an important discussion point and should not be generalized as cells have different responses, Mishra said.

“Clearly neutrophils have cytotoxic oxygen radicals, but they also have a lot of growth factors including vascular endothelial growth factor,” he said. “Mononuclear cells are generally considered reparative cells, and when you take platelets and put them in close quarters with these white blood cells, they act differently.”

A classification system

Mishra noted that he has created a classification system in which PRP types I and II have white blood cells above baseline, and PRP types III and IV have minimal or no white blood cells. Unlike PRP types II and IV, PRP types I and III are not activated.

“It is clearly not ideal, but I am suggesting it as a place to start,” Mishra said. He expects his work on a classification system to be published this year.

The future of PRP may include specific types of PRP with different formulations and concentrations of white blood cells. This includes the potential discovery of a common mechanistic pathway and innovation to go beyond musculoskeletal indications.

“PRP is a simple concept,” Mishra said. “I think there is an unfortunately complex set of questions that need to be answered. We should have data driving present and future applications.” – by Robert Press

Reference:

• Mishra A. PRP, History, classification and horizons. Presented at the 2011 Annual Meeting of the Arthroscopy Association of North America. April 14-16. San Francisco.

• Allan Mishra, MD, can be reached at Stanford University Medical Center/Menlo Medical Clinic,1300 Crane St., Menlo Park, CA 94025; 650-498-6645; email: am@totaltendon.com.
• Disclosure: Mishra receives royalties from Biomet Biologics and owns stock in BioParadox.